A Comparison between Term-Independence Retrieval Models for Ad Hoc Retrieval

2022 ◽  
Vol 40 (3) ◽  
pp. 1-37
Author(s):  
Edward Kai Fung Dang ◽  
Robert Wing Pong Luk ◽  
James Allan

In Information Retrieval, numerous retrieval models or document ranking functions have been developed in the quest for better retrieval effectiveness. Apart from some formal retrieval models formulated on a theoretical basis, various recent works have applied heuristic constraints to guide the derivation of document ranking functions. While many recent methods are shown to improve over established and successful models, comparison among these new methods under a common environment is often missing. To address this issue, we perform an extensive and up-to-date comparison of leading term-independence retrieval models implemented in our own retrieval system. Our study focuses on the following questions: (RQ1) Is there a retrieval model that consistently outperforms all other models across multiple collections; (RQ2) What are the important features of an effective document ranking function? Our retrieval experiments performed on several TREC test collections of a wide range of sizes (up to the terabyte-sized Clueweb09 Category B) enable us to answer these research questions. This work also serves as a reproducibility study for leading retrieval models. While our experiments show that no single retrieval model outperforms all others across all tested collections, some recent retrieval models, such as MATF and MVD, consistently perform better than the common baselines.

Author(s):  
Souria Ortiga

During the 1980s, and despite its maturity, the search information (RI) was only intended for librarians and experts in the field of information. Such tendentious vision prevailed for many years. Since the mid-90s, the web has become an increasingly crucial source of information , which has a renewed interest in IR. In the last decade, the popularization of computers, the terrible explosion in the amount of unstructured data, internal documents, and corporate collections, and the huge and growing number of internet document sources have deeply shaken the relationship between man and information. Today, a great change has taken place, and the RI is often used by billions of people around the world. Simply, the need for automated methods for efficient access to this huge amount of digital information has become more important, and appears as a necessity.


2017 ◽  
Vol 60 ◽  
pp. 1127-1164 ◽  
Author(s):  
Ran Ben Basat ◽  
Moshe Tennenholtz ◽  
Oren Kurland

The main goal of search engines is ad hoc retrieval: ranking documents in a corpus by their relevance to the information need expressed by a query. The Probability Ranking Principle (PRP) --- ranking the documents by their relevance probabilities --- is the theoretical foundation of most existing ad hoc document retrieval methods. A key observation that motivates our work is that the PRP does not account for potential post-ranking effects; specifically, changes to documents that result from a given ranking. Yet, in adversarial retrieval settings such as the Web, authors may consistently try to promote their documents in rankings by changing them. We prove that, indeed, the PRP can be sub-optimal in adversarial retrieval settings. We do so by presenting a novel game theoretic analysis of the adversarial setting. The analysis is performed for different types of documents (single-topic and multi-topic) and is based on different assumptions about the writing qualities of documents' authors. We show that in some cases, introducing randomization into the document ranking function yields an overall user utility that transcends that of applying the PRP.


Cryptography ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 10
Author(s):  
Niluka Amarasinghe ◽  
Xavier Boyen ◽  
Matthew McKague

The modern financial world has seen a significant rise in the use of cryptocurrencies in recent years, partly due to the convincing lure of anonymity promised by these schemes. Bitcoin, despite being considered as the most widespread among all, is claimed to have significant lapses in relation to its anonymity. Unfortunately, studies have shown that many cryptocurrency transactions can be traced back to their corresponding participants through the analysis of publicly available data, to which the cryptographic community has responded by proposing new constructions with improved anonymity claims. Nevertheless, the absence of a common metric for evaluating the level of anonymity achieved by these schemes has led to numerous disparate ad hoc anonymity definitions, making comparisons difficult. The multitude of these notions also hints at the surprising complexity of the overall anonymity landscape. In this study, we introduce such a common framework to evaluate the nature and extent of anonymity in (crypto) currencies and distributed transaction systems, thereby enabling one to make meaningful comparisons irrespective of their implementation. Accordingly, our work lays the foundation for formalizing security models and terminology across a wide range of anonymity notions referenced in the literature, while showing how “anonymity” itself is a surprisingly nuanced concept, as opposed to existing claims that are drawn upon at a higher level, thus missing out on the elemental factors underpinning anonymity.


1970 ◽  
Vol 24 (3) ◽  
pp. 479-502 ◽  
Author(s):  
R. L. Friedheim ◽  
J. B. Kadane

International arrangements for the uses of the ocean have been the subject of long debate within the United Nations since a speech made by Ambassador Arvid Pardo of Malta before the General Assembly in 1967. Issues in question include the method of delimiting the outer edge of the legal continental shelf; the spectrum of ocean arms control possibilities; proposals to create a declaration of principles governing the exploration for, and the exploitation of, seabed mineral resources with the promise that exploitation take place only if it “benefits mankind as a whole,” especially the developing states; and consideration of schemes to create international machinery to regulate, license, or own the resources of the seabed and subsoil. The discussions and debates began in the First (Political and Security) Committee of the 22nd General Assembly and proceeded through an ad hoc committee to the 23rd and 24th assembly plenary sessions. The creation of a permanent committee on the seabed as a part of the General Assembly's machinery attests to the importance members of the United Nations attribute to ocean problems. Having established the committee, they will be faced soon with the necessity of reaching decisions. The 24th General Assembly, for example, passed a resolution requesting the Secretary-General to ascertain members' attitudes on the convening of a new international conference to deal with a wide range of law of the sea problems.


Author(s):  
Dr. B. Balakumar

Abstract: Recent advances in software, hardware communication technologies are enabling the design and implementation of whole range of different type of network that are various environments. Vehicular Ad-Hoc network is received a lot of interest in the couple years in the one of the networks. A Vehicular Ad-Hoc Network or VANET is a technology that uses moving cars as nodes in a network to create a mobile network. In VANET improving the driving comfort and safety information message are broadcasted regularly. VANET turns every participating car approximately 100 to 300 meters to connect and turn create network with a wide range. In enable vehicle to communicate which other with roadside units (RSUs). Vehicular network are special types of VANET that supported infrastructure based real time traffic management, including internet access, video streaming and content distribution. Privacy - preserving data Acquisition and forwarding scheme by introducing the novel cryptographic algorithm for key generation and powerful encryption. This paper introduces system that takes Advantages of the RSUs that are the connected to the internet provide various types of information to VANET users. Keywords: VANET, RSU, Ad-Hoc Network, URE, ITS


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